Everyone knows about reward systems in the brain.

Today we meet the hero of the often-neglected anti-reward system.

Habenula anatomy and function… The habenula is a tiny, pea-sized structure that sits atop the pineal gland.

On coronal images you can find it bulging into the 3rd ventricle right above the posterior commissure.

Fastigial Nucleus: the most important structure you’ve never heard of.

6 points on anatomy and function. 1. The FN is a tiny structure that lies deep near the midline of the cerebellum, right above the 4th ventricle.

Our lab’s Friday neuroanatomy series is back in action.

Today we cover a tiny thalamic nucleus, but with a huge influence on thalamocortical processing and consciousness.

3 things to know about thalamic reticular nucleus (TRN)… 1. Anatomy. The anatomy is simple. TRN is like a thin shell surrounding the thalamus.
From in to out: thalamus, external medullary lamina (white matter, in red), TRN (green), and internal capsule (IC).

STN serves as the brain's primary pincushion for DBS.

But it has important and fascinating functions beyond that.

Subthalamic nucleus anatomy and function thread… STN is a little smaller than an M&M. It lives in a crowded neighborhood of important structures.

Notable landmarks:
The thalamus is just above.
Substantia nigra of the midbrain is just below.
Internal capsule is just lateral.

A fear center? A threat detection system?

What does the amygdala do?

🧵 on amygdala anatomy and function. The amygdala is about the size of an almond.

The basal nucleus of the amgydala has the shape of an almond, which is where it gets its Latin name.

Does human consciousness rely on this tiny wisp of gray matter?

Claustrum anatomy and function 🧵 Francis Crick, winner of a Nobel Prize for co-discovery of DNA structure, made his final scientific contribution from his death bed.

He boldly proposed the claustrum is integral to multisensory binding that underlies our perceptual experiences.

Did he and Koch get it right?

A white matter tract that takes 30 years to mature must be doing something important.

3 things to know about the uncinate fasciculus. 1. UF is bidirectional, connecting the ventral frontal and anterior & medial temporal lobe.

Uncinate means ‘hook’ and the arch of the hook tracks along the temporal stem (red arrow) and is located just below the inferior fronto-occipital fasciculus (IFOF)...

Arguably the most important white matter tract supporting human cognition.

5 things about arcuate fasciculus anatomy and an argument for its critical role in human cognition. 1) Arcuate = arched. Its classic arched appearance directly connects the lateral prefrontal cortex and temporal lobe. There is an indirect path with a stop in the inferior parietal lobe.

Why is the insula the most interesting region in the brain?

Here are 6 things worth knowing. This is topic #3 for our lab's Friday 'Ode to Neuroanatomy' series. Insula is Latin for island, which connotes detachment & isolation. It was a botched naming job in some respects, as the insula is an exceedingly well connected anatomical hub.

Damage to this major occipitotemporal white matter tract can be associated with all except:

A) Inability to recognize faces
B) Inability to read
C) Monotone, emotionally flat speech
D) Lack of emotion to visual objects, including loved ones C. That is the inferior longitudinal fasciculus (ILF), a key tract for the 'what' ventral visual pathway.
Critical for recognizing visual objects and relating them to conceptual knowledge.

A white matter lesion causes difficulty coming up with the names of items & frequent semantic errors. The responsible structure (red) is most likely…

A. Arcuate fasciculus
B. Inferior longitudinal fasc.
C. Inferior fronto-occipital fasc.
D. Superior longitudinal fasc. C. IFOF.

There is a narrow bottleneck of IFOF between ventral putamen and insula, such that a small lesion can disrupt a major anterior-posterior ventral white matter tract. IFOF is critical for semantic cognition, linking words & objects to conceptual knowledge.

We see some strange and sometimes paradoxical effects of lesions to the default mode network.

A thread of some of the curious observations…. DMN is located as far away from primary motor and sensory cortices as possible –anatomically buffered from external reality and perfectly positioned to support stimulus-independent thought… simulating situations, replaying events, planning, ruminating.
pnas.org/doi/10.1073/pn…

Is the wakefulness-promoting, consciousness-enabling influence of the brainstem left-lateralized in humans? Seems unlikely, right? In 2016 we did a lesion study of coma and our results suggested a left lateralization to a dorsolateral pontine tegmentum arousal-promoting region.

This was a small enough sample I think we all assumed the apparent laterality could have been by chance.

@NickTrapp13 and our team evaluated depression symptoms in 526 people with focal brain lesions.

The 5 most important things we learned… 🧵 1) Increased depression was seen after lesions of the insula –right insula was strongest association of anywhere in the brain.

35 patients with precuneus lesions evaluated to date… here’s what we’re learning so far. 🧵 For context, part of the motivation for this line of research was to evaluate long-standing speculation that the precuneus has an important role in consciousness.

Is it warranted?

This is an amazing story – Krista and Tatiana Hogan are conjoined twin sisters with distinct personalities and *mostly* separate brains that are linked by a ‘thalamic bridge.’ They can use it as a portal to access the other’s sensations and feelings. 👇 Tatiana doesn’t like ketchup and gets annoyed when Krista eats it because she will taste it too.

They can access visual information from the other's eyes and move the other’s limbs. Some modalities are apparently easier to access than others, with vision being more difficult.

The individual with this precuneus lesion experienced a dramatic change in how he perceived the passage of time after surgery of a glioma.

Minutes felt like hours… each time he would check his watch he’d be surprised how little time had passed. 👇 A second person with a very similar lesion reported the same. There was a disorientation to time accompanied by a feeling like “time did not run.” It was even difficult to conceptualize what time was.